// GZipOutputStream.cs
//
// Copyright (C) 2001 Mike Krueger
//
// This file was translated from java, it was part of the GNU Classpath
// Copyright (C) 2001 Free Software Foundation, Inc.
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
// 
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent
// modules, and to copy and distribute the resulting executable under
// terms of your choice, provided that you also meet, for each linked
// independent module, the terms and conditions of the license of that
// module.  An independent module is a module which is not derived from
// or based on this library.  If you modify this library, you may extend
// this exception to your version of the library, but you are not
// obligated to do so.  If you do not wish to do so, delete this
// exception statement from your version.

using System;
using System.IO;
using ICSharpCode.SharpZipLib.Checksums;
using ICSharpCode.SharpZipLib.Zip.Compression;
using ICSharpCode.SharpZipLib.Zip.Compression.Streams;

namespace ICSharpCode.SharpZipLib.GZip 
{
    
    /// <summary>
    /// This filter stream is used to compress a stream into a "GZIP" stream.
    /// The "GZIP" format is described in RFC 1952.
    ///
    /// author of the original java version : John Leuner
    /// </summary>
    /// <example> This sample shows how to gzip a file
    /// <code>
    /// using System;
    /// using System.IO;
    /// 
    /// using ICSharpCode.SharpZipLib.GZip;
    /// using ICSharpCode.SharpZipLib.Core;
    /// 
    /// class MainClass
    /// {
    ///     public static void Main(string[] args)
    ///     {
    ///             using (Stream s = new GZipOutputStream(File.Create(args[0] + ".gz")))
    ///             using (FileStream fs = File.OpenRead(args[0])) {
    ///                 byte[] writeData = new byte[4096];
    ///                 Streamutils.Copy(s, fs, writeData);
    ///             }
    ///         }
    ///     }
    /// }   
    /// </code>
    /// </example>
    public class GZipOutputStream : DeflaterOutputStream
    {
        enum OutputState
        {
            Header,
            Footer, 
            Finished,
            Closed,
        };

        #region Instance Fields
        /// <summary>
        /// CRC-32 value for uncompressed data
        /// </summary>
        protected Crc32 crc = new Crc32();
        OutputState state_ = OutputState.Header;
        #endregion

        #region Constructors
        /// <summary>
        /// Creates a GzipOutputStream with the default buffer size
        /// </summary>
        /// <param name="baseOutputStream">
        /// The stream to read data (to be compressed) from
        /// </param>
        public GZipOutputStream(Stream baseOutputStream)
            : this(baseOutputStream, 4096)
        {
        }
        
        /// <summary>
        /// Creates a GZipOutputStream with the specified buffer size
        /// </summary>
        /// <param name="baseOutputStream">
        /// The stream to read data (to be compressed) from
        /// </param>
        /// <param name="size">
        /// Size of the buffer to use
        /// </param>
        public GZipOutputStream(Stream baseOutputStream, int size) : base(baseOutputStream, new Deflater(Deflater.DEFAULT_COMPRESSION, true), size)
        {
        }
        #endregion
    
        #region Public API
        /// <summary>
        /// Sets the active compression level (1-9).  The new level will be activated
        /// immediately.
        /// </summary>
        /// <param name="level">The compression level to set.</param>
        /// <exception cref="ArgumentOutOfRangeException">
        /// Level specified is not supported.
        /// </exception>
        /// <see cref="Deflater"/>
        public void SetLevel(int level)
        {
            if (level < Deflater.BEST_SPEED) {
                throw new ArgumentOutOfRangeException("level");
            }
            deflater_.SetLevel(level);
        }
        
        /// <summary>
        /// Get the current compression level.
        /// </summary>
        /// <returns>The current compression level.</returns>
        public int GetLevel()
        {
            return deflater_.GetLevel();
        }
        #endregion
        
        #region Stream overrides
        /// <summary>
        /// Write given buffer to output updating crc
        /// </summary>
        /// <param name="buffer">Buffer to write</param>
        /// <param name="offset">Offset of first byte in buf to write</param>
        /// <param name="count">Number of bytes to write</param>
        public override void Write(byte[] buffer, int offset, int count)
        {
            if ( state_ == OutputState.Header ) {
                WriteHeader();
            }

            if( state_!=OutputState.Footer )
            {
                throw new InvalidOperationException("Write not permitted in current state");
            }

            crc.Update(buffer, offset, count);
            base.Write(buffer, offset, count);
        }
        
        /// <summary>
        /// Writes remaining compressed output data to the output stream
        /// and closes it.
        /// </summary>
        public override void Close()
        {
            try {
                Finish();
            }
            finally {
                if ( state_ != OutputState.Closed ) {
                    state_ = OutputState.Closed;
                    if( IsStreamOwner ) {
                        baseOutputStream_.Close();
                    }
                }
            }
        }
        #endregion
        
        #region DeflaterOutputStream overrides
        /// <summary>
        /// Finish compression and write any footer information required to stream
        /// </summary>
        public override void Finish()
        {
            // If no data has been written a header should be added.
            if ( state_ == OutputState.Header ) {
                WriteHeader();
            }

            if( state_ == OutputState.Footer)
            {
                state_=OutputState.Finished;
                base.Finish();

                uint totalin=(uint)(deflater_.TotalIn&0xffffffff);
                uint crcval=(uint)(crc.Value&0xffffffff);

                byte[] gzipFooter;

                unchecked
                {
                    gzipFooter=new byte[] {
                    (byte) crcval, (byte) (crcval >> 8),
                    (byte) (crcval >> 16), (byte) (crcval >> 24),
                    
                    (byte) totalin, (byte) (totalin >> 8),
                    (byte) (totalin >> 16), (byte) (totalin >> 24)
                };
                }

                baseOutputStream_.Write(gzipFooter, 0, gzipFooter.Length);
            }
        }
        #endregion
        
        #region Support Routines
        void WriteHeader()
        {
            if ( state_ == OutputState.Header ) 
            {
                state_=OutputState.Footer;

                int mod_time = (int)((DateTime.Now.Ticks - new DateTime(1970, 1, 1).Ticks) / 10000000L);  // Ticks give back 100ns intervals
                byte[] gzipHeader = {
                    // The two magic bytes
                    (byte) (GZipConstants.GZIP_MAGIC >> 8), (byte) (GZipConstants.GZIP_MAGIC & 0xff),

                    // The compression type
                    (byte) Deflater.DEFLATED,

                    // The flags (not set)
                    0,

                    // The modification time
                    (byte) mod_time, (byte) (mod_time >> 8),
                    (byte) (mod_time >> 16), (byte) (mod_time >> 24),

                    // The extra flags
                    0,

                    // The OS type (unknown)
                    (byte) 255
                };
                baseOutputStream_.Write(gzipHeader, 0, gzipHeader.Length);
            }
        }
        #endregion
    }
}
